The present invention relates to radio frequency test equipment, and more particularly, is directed to a coupler for use in a test enclosure and for coupling to test equipment to enable wireless communication with a device under test.
Wireless communication equipment are subject to various standards relating to wireless transmission, including but not limited to power emissions standards and interference standards. The four main cellular frequency bands cover 824 to 960 MHz and 1710 to 1990 MHz. Bluetooth, Wireless LAN (WLAN) and/or global positioning system (GPS) functionality is being added to many wireless products; the center frequencies of these systems are 2450 MHz and 1575 MHz respectively. Such wireless devices, e.g., cellphones, personal digital assistants (PDAs) and smart phones, must be tested prior to sale, to ensure they comply with appropriate standards, and in general, function properly.
FIG. 1A shows a typical radio frequency (RF) testing enclosure. A device under test is placed in an enclosure that contains a coupler for wirelessly coupling between test equipment and the device under test.
Conventional couplers are designed to operate over specific frequency bands. Accordingly, when testing a device designed to operate at several frequency bands, the testing procedure must include switching the coupler for each of the frequency bands being tested. The need to switch between different couplers to test the same device decreases the reliability and repeatability of tests, increases the cost of testing, increases the difficulty of calibrating the tests, and increases the test time.
Thus, there is a need for a wide bandwidth RF coupler, operating in several frequency bands.